Note 17 - Warrant Liabilities - Warrant Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Jan. 17, 2018
Proceeds allocated to warrant liabilities	$ 135	$ 1,327	$ 135	$ 1,327	$ 956	$ 606	$ 801	$ 2,275
Change in fair value of warrants	(821)	526	(471)	(948)
Investor Warrants [Member]
Proceeds allocated to warrant liabilities	32	1,103	32	1,103	793	503	664	1,890
Change in fair value of warrants	(761)	439	(471)	(787)
Placement Agent Warrants [Member]
Proceeds allocated to warrant liabilities	103	224	103	224	$ 163	$ 103	$ 137	$ 385
Change in fair value of warrants	$ (60)	$ 87		$ (161)